<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    let year=+prompt(`输入年份呀`)
    let month=+prompt(`输入月份呀`)
    if(month===1||month===3||month===5||month===7||month===8||month===10||month===12){
      document.write(`这个月有${31}天`)
    }
    else if(month===4||month===6||month===9||month===11){
      document.write(`这个月有${30}天`)
    }else if(month===2){
      if(year%4===0&&year%100!==0||year%400===0){
        document.write(`这个月有${29}天`)
      }else{
        document.write(`这个月有${28}天`)
      }
}
    else{
      document.write('输入正确的东西撒')
    }
    
console.log(11&&22)
    </script>
</body>
</html>